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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Copyright (C) 2001 Gerwin Klein <lsf@jflex.de> *
* Copyright (C) 2001 Bernhard Rumpe <rumpe@in.tum.de> *
* All rights reserved. *
* *
* License: BSD *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
import java.util.*;
/**
* Symbol table for the interpreter, contains information about
* variables and functions.
*
* For every binding location of a name a symbol will be created.
* The symbol tables are connected hierarchically by pointers to
* the predecessor. Lookup takes predecessors into account.
*/
public class SymTab {
Map<String,SymtabEntry> m; // contains the list of words
SymTab pred; // predecessor symbol table (if exists)
public SymTab() {
this(null);
}
public SymTab(SymTab p) {
m = new HashMap<String,SymtabEntry>();
pred = p;
}
public boolean enter(String s, SymtabEntry e) {
Object value = lookup(s);
m.put(s, e);
return(value==null);
}
public SymtabEntry lookup(String s) {
SymtabEntry value = m.get(s);
if (value==null && pred!=null)
value = pred.lookup(s);
return value;
}
public String toString() { // for output with print
StringBuilder res = new StringBuilder("symbol table\n=============\n");
for (Map.Entry<String,SymtabEntry> entry : m.entrySet())
res.append(entry.getKey()).append(" \t").append(entry.getValue()).append("\n");
if (pred != null)
res.append("++ predecessor!\n");
return res.toString();
}
public int size() {
return(m.size());
}
}
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